In light of emerging plastic recycling techniques, large amounts of endocrine disruptive phthalates are expected to become available in the near future as hazardous waste streams. These legacy additives have been dominating the global plasticizer market; however they are currently being replaced by safer alternatives, such as 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH). Here, we report the upcycling of real polyvinyl chloride (PVC) waste-extracted phthalate plasticizers, via a one-pot (trans)esterification - hydrogenation process. To that end, model hydrogenations of historically relevant phthalates were first evaluated, where Ru/Al2O3 in combination with green ether solvents emerged as a highly effective catalytic system, yielding &gt; 99% ring-hydrogenated products under mild conditions. However, selective hydrogenolysis of benzyl-oxygen bonds, present in benzyl butyl phthalate, complicated the hydrogenation of real plasticizer fractions, as the formed benzoic acid strongly inhibits the hydrogenation of other phthalates in the mixture. Therefore, the hydrogenation was supplemented with a (trans)esterification in long-chain alcohol solvents, resulting in the smooth and complete hydrogenation of all phthalates (0.1 mol% Ru, 5 mol% H2SO4, 140 °C, 50 bar H2 for 240 minutes). Further efforts were directed towards real plasticizer waste extracts by evaluating the effects of some expected feed impurities on the kinetics of the hydrogenation reaction, such as co-extracted plasticizers and residual PVC. Acquired process insights were then implemented on crude PVC waste-extracted plasticizer fractions, eventually yielding the complete upcycling of end-of-life phthalate plasticizers after a thorough treatment of the extract with activated carbon. In a final stage, the extract-spent Ru-catalyst and activated carbon sample were characterized in order to gain a deeper understanding of the trace contaminations present in the extract, which were responsible for the initial catalytic inhibitory effects.

Upcycling of plastic waste-extracted phthalate esters into safe plasticizers analogues

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.